Pressure vessels for sample concentration or desalting, for example, may use air pressure as the driving force to effect separation, such as through a suitable membrane. Typically outer support housings are containment frames are necessary to contain the vessel when under pressure, hold the cover on the vessel, help prevent premature or accidental release of the cover, as well as to add strength to the assembly when pressurized. However, filtration is complete, it is often very difficult to remove the vessel from the support housing. In addition, if the vessel was attempted to be pressurized without the support housing in place, the cover would blow off.
One exemplary application of such pressure vessels are stirred cell devices. Conventional stirred cells provide pressure-based sample concentration or desalting, such as of samples containing proteins and viruses. Such devices use pressure as the driving force to force fluid through a membrane while retaining and concentrating the macromolecules too large to pass through the membrane. Typically the membrane is an ultrafiltration membrane. Desalting is achieved by a process of diafiltration where fluids are replaced and the system is re-pressurized. Conventional stirred cells can include gentle magnetic stirring to control the concentration polarization or accumulation of macromolecules on the surface of the membrane, and to minimize shear stress-induced denaturation. The devices are designed for rapid concentration or purification of macromolecular solutions, and can typically handle volumes of from 3 mls to 1000 mls.
The ultrafiltration membranes used in such stirred cells are size exclusion membranes; due to the extremely small pores, a substantial driving force is required to effect the separation. Exemplary driving forces sufficient to create high enough force to push the liquid through the membrane are centrifugation and air pressure. Air pressures of less than 75 psi are usually sufficient.
In addition to the shortcomings of such pressure vessels mentioned above, additional shortcomings specific to stirred cell devices can include the magnetic stir bar contacting and damaging the membrane; the use of non-standard connectors; fragile vent valve parts that are prone to breakage; and caps that are difficult to open and close; and possible system leakage.
It would be desirable to eliminate the containment frame, and provide appropriate venting, pressure relief, and a safety interlock in pressure vessels.